ES2260663T3 - PRODUCT FOR THE TREATMENT OF WATER AND WASTEWATER AND A PROCEDURE TO PRODUCE THIS PRODUCT. - Google Patents

Abstract

The present invention relates to a product for the treatment of water and wastewater and a process for producing said product. Said product comprises high cationic starch powder and a brine solution comprising sea water and/or salts comprising two-valent ions. The salts are preferably CaCl2 and/or Ca(N03)2 and/or MgCl2. The concentration of the brine solution is 5 - 50 g/l, preferably 10 - 40 g/l. The starch is preferably potato starch and has > 10 % charge density (degree of substitution). The starch concentration is 5 - 25 weight %, preferably 15 - 25 weight %. The viscosity is 300 - 10000 cP (mPa s), preferably 1000 - 5000 cP (mPa s). The product for the treatment of water and wastewater is produced by feeding a high cationic starch powder gradually into a brine solution using a high shear mixer.

Description

Water and water treatment product residuals and a procedure to produce said product.

The present invention relates to a product for the treatment of water and wastewater and a procedure for the production of said product.

The chemical treatment of wastewater It includes coagulation and flocculation. In the phase of coagulation, the particles can be destabilized by electrostatic neutralization of the particle surface and A few particles are assembled into microflocules. By means of the flocculation, larger aggregates of microflocles from macrophages, which can quickly be separated from the aqueous phase by for example sedimentation or instantaneous flotation.

In municipal treatment plants and industrial, most of the chemical treatment is carried out with inorganic metal salts (iron chloride, iron sulfate, aluminum chloride, previously polymerized aluminum chloride, etc.). In addition, synthetic cationic polymers such as polyamine and polydiallyldimethylammonium chloride (poly-DADMAC) are used as coagulants alone or in combination with metal salts. In addition, some biopolymers cationics, such as chitosan, for example, are used as coagulants The pH adjustment and the addition of inorganic particles to obtain coagulation and flocculation. The variants of cationic, anionic and non-ionic polyacrylamides are used as flocculation aids.

Metal salts suffer from the inconvenience of that metal ions react with water and form hydroxide of metal For example, Fe 3+ will form Fe (OH) 3, which will cause an increase significant in sludge production, both in volume and in dry solids An increased sludge production leads to costs increases related to sludge treatment, the handling and eventually deposition. The mud formed with Metal salts is less suitable as soil improvement agent in agriculture, due to possible heavy metal residues and the Covalent phosphate bond with metal ions. The salts of metal may also not provide the desired effect in some water or wastewater qualities due to, for example, pH, alkalinity, fat / oil content and solids characteristics suspended In some situations a high dose is required unreasonable metal salts to achieve the desired effect.

Metal chlorides are corrosive and lead to increased costs related to corrosion in plants and in the main system. Metal sulfates can lead to problems related to the formation of hydrogen sulfide Biological under anaerobic conditions. In some situations there are also regulations on the discharge of sulfate ions and ions chloride. Chloride ions are harmful in concentrations too high.

There are issues related to use of synthetic polymers due to the effects ecotoxicological in the environment in addition to health and Safety related to the handling of these products. The synthetic polymers such as polyamine and poly-DADMAC could not decompose sufficiently  and high concentrations in the mud could have an effect negative on soil structure and absorption by plants when the sludge is used as an agent to improve ground. In addition, the products are relatively expensive.

Polyacrylamide usually has a high resistance to biological degradation and products commercials should be marked as carcinogenic, due to Acrylamide residues in products.

Water and wastewater treatment with Starch is known in the art, and it would be of interest to use modified cationic starch. The modified starch is composed of native starch, which is a pure and renewable natural product. By cationization, the charged groups bind to the starch native, which makes it suitable as a coagulant / flocculant, and It is also possible to biologically decompose cationic starch. This makes it more suitable than synthetic polymers and salts. metal when the sludge is used as an agent for the improvement of soil and also provides better conditions for the discharge of treated water to the container. The cationic starch modification provides starch with better efficacy and is an effective solution in cost compared to synthetic polymers due to a dose lower and also compared with metal salts due to a reduced sludge production Modified starch presents also better overall performance than polymers synthetic and metal salts on some water qualities and of sewage It seems to operate as both coagulant and flocculant

When starch powder disperses in the aqueous phase, the starch particles initially swell by humidifying and absorbing water. This is a slow procedure that increases by temperature. Normally, the starch is therefore dissolved by cooking at 95 ° C for between 30 and 60 minutes. When the particles of starch are well swollen, individual polymer chains they begin to untangle and the solution will appear more or less clear. When the solution cools to room temperature, it procedure can be partially reversed leading to an aspect opaque solution. Since there are large related costs with heating and cooking the solution in addition to time and of the required volumes, it would be of interest to find a procedure to modify starch without having to heat / cook the starch solution, as this would make the use of cationic starch as a coagulant one more solution Easy and cheaper.

EP 0 737 210 B1 refers to a process for the production of cationic starch derivatives in the form of an aqueous solution, in which the structure of the molecule Starch is modified by oxidation before the stage of cationization The solids of the reaction mixture during Cationization reaction is maintained above 50%, advantageously greater than 55%. The starch is added to the mixture of reaction in powdered or mud form before the stage of Cationization and cleavage of starch is carried out with the help of an oxidant (peroxide). The cationizing chemical is preferably chloride of 2,3-epoxypropyltrimethylammonium. The procedure described in this patent provides relatively high costs and It is not very ecological due to the use of chemical products to oxidize starch molecules. NaOH is added during Cationization and this will provide a final product with a pH high that must be handled carefully.

WO 99/61377 refers to a procedure for the treatment of aqueous streams that They comprise biosolids. A procedure that can be provided is provided. use to substantially clarify aqueous streams and optionally separate biosolids, especially proteins, to from food processing operations, which includes contacting an aqueous stream comprising biosolids with an anionic colloid and an organic polymer, to flocculate the biosolids Cationic starch can be used in combination with the metal and / or silica salts activated, but the starch is not Modify before use.

Remmer, J. and Eklund, D., Wochenbl. Papierfabr., 119, No. 21; 855-859 (Nov 15, 1991) describes the absorption of starch in surface gluing. The main parameter that influences the dynamic absorption of Starch size during surface gluing is the viscosity of the starch solution, regardless of the viscosity adjustment procedure used (drying or modification of the length of the macromolecular chain). The viscosity is also the temperature dependent variable dominant.

The main objective of the present invention was to reach a product for water and water treatment residuals, which would provide an improvement in water treatment and wastewater and thus an improved quality of Water.

Another objective was that the product should be based on a natural, ecological and biodegradable product.

An additional objective was that the product It should be safe for handling, it should have a neutral pH and not contain toxic components in itself or by degradation.

An additional objective was to obtain a product, which would provide low treatment costs.

It was also an objective of the present invention obtain a method of producing a product for  water and wastewater treatment, which would provide low production costs

These and other objectives of the present invention they were achieved by product and procedure as described below. The present invention is characterized further by the patent claims.

The product consists of a starch powder Highly cationic with> 10% charge density (degree of substitution) dissolved in a brine solution. In principle, it You can use any native starch. It was found that the dust starch could preferably be potato starch and the most preferred concentration was found to be comprised between 15 and 25% by weight. It was surprisingly found that when they used salts that have ions of two valences, it was possible obtain the desired starch solution. Brine solution it can be seawater, CaCl2, Ca (NO3) 2, MgCl2, etc., or mixtures thereof. Viscosity should be <10,000 cP (mPa s) at temperatures> 15 ° C. How much more high is the concentration of the brine solution, more Starch powder will easily dissolve.

The highly concentrated starch solution should preferably comprise> 10 g / l of mineral salts of seawater, CaCl 2, Ca (NO 3) 2, MgCl2, etc., or mixtures thereof and> 5% by weight of starch powder with charge density (degree of substitution)> 10% The starch solutions had a pH in the range of 4 to 8.

Product quality was controlled by final viscosity and functionality as a coagulant and flocculant by removing particle in water treatment residual Functionality tests were carried out. by standard jar tests in which they were added specific amounts of starch solution to a sample of 1 liter wastewater and turbidity or solids content suspended from the clear aqueous phase was measured after the flocculation and sedimentation. The test conditions of jug were 30 sec mixing at high speed (500 rpm), 10 min mixing at low speed (50 rpm) and 15 min of sedimentation.

It was found that a mixer could be used of high shear to mix starch powder and a brine solution to produce a starch solution highly concentrated with excellent properties such as coagulant / flocculant for water treatment. The dust of starch was gradually fed into the brine solution using the high shear mixer.

Treatment with a shear mixer elevated was initially used to cut polymer chains in shorter units, as this proved to be more favorable for synthetic coagulants in previous studies. The effect of high shear mixer is observed due to viscosity reduced in the polymer solution and it is assumed that this is caused by the degradation of macromolecules. The mixer of high shear can also have other effects and one can be that promotes the dissolution procedure. If so, you can it is not necessary to cook the starch solution and then the Use of cationic starch as a coagulant will be a solution Easier and more economical.

The function of the high shear mixer was to generate an effective coagulant to cut the chain of the starch macromolecule to reduce the viscosity of the solution at a level useful for the application (<10,000 cP (mPa s)).

The function of the brine solution was prepare the starch solution more easily, be able to produce the high concentration solution, have an effect positive in product stability and have a positive effect in the function of the product as a coagulant.

The function of gradual powder feeding was to optimize the function of the high shear machine maintaining the viscosity within a level that resulted in a cut effective starch and be able to produce a solution of high concentration

The present invention will comprise in its broadest scope a product for the treatment of water and wastewater, wherein said product comprises a highly cationic starch powder and a brine solution comprising seawater and / or salts comprising ions of two valences. The salt can be CaCl 2 and / or Ca (NO 3) 2 and / or MgCl 2. The concentration of the brine solution is 5-50 g / l, preferably 10 to 40 g / l. The cationic starch powder has> 10% charge density (degree of substitution). The starch powder is preferably potato starch and the starch concentration is 5 to 25% by weight, preferably 15 to 25% by weight. The viscosity is between 300 and 10,000 cP (mPa s), preferably between 1,000 and 5,000 cP
(mPa s).

The present invention further comprises a procedure to produce a product for water treatment and wastewater, in which a starch powder is mixed highly cationic and a brine solution comprising seawater and / or salts comprising ions of two valences in a high shear mixer to maintain viscosity < 10000 cP (mPa s) at temperatures> 15 ° C. Viscosity is maintained preferably at 1000-5000 cP (mPa s). The powder to liquid feed rate is> 100 kg / m 3 h. The production temperature is 50 to 100ºC, preferably from 60 to 80 ° C.

The present invention is described and explained. also in the following figures and examples.

Fig. 1 shows a system for production of a highly concentrated starch solution.

Fig. 2 shows the relationship between the starch concentration and viscosity at temperatures different.

Fig. 3 shows the comparison of the functionality of various starch solutions (5-20% by weight) in seawater and CaCl2, respectively.

Fig. 4 shows the comparison of the functionality of a starch solution at 18% by weight on scale industrial with an in-line mixer and a 0.5% solution by weight produced on a laboratory scale in a beaker of 1 liter.

Fig. 5 shows the relationship between the time of treatment, temperature and viscosity for a production at industrial scale of a 15% by weight starch solution.

Fig. 1 shows a production plant for the production of highly concentrated starch solutions. Starch powder is carried from a larger system of storage of powder 1 to a high shear mixer 2 in which a brine solution is gradually fed, which is leads to a raised shear mixer 2 from a tank mix / reserve 3 equipped with a mixer 4 and a device cooling 5. The central part of the production plant is the high shear mixer 2. The shear mixer raised 2 should preferably be an in-line turbo mixer with high shear forces in which the liquid and dust are mix immediately and effectively. Shear forces must be sufficient to maintain viscosity <10,000 cP (mPa s) at temperatures> 15ºC with a feed rate of powder to liquid of> 100 kg / m 3 h. This requires a mixer high shear with a power> 15 kW. Temperature of the starch solution increases with increasing concentration in production The production device that includes a raised shear mixer 2 should be able to work at temperatures up to 70-100ºC. The high temperature is positive for dissolution efficiency and Product stability The production temperature should be> 50 ° C, preferably 60-80 ° C.

The starch solution is recirculated in the raised shear mixer 2 via mixing / reserve tank 3. Recirculation can be facilitated by the mixer raised shear 2 or by an extra pump 6. In the tank mix / reserve 3 the liquid must be mixed vigorously to achieve a homogeneous solution and ensure that the volume of Whole liquid is sufficiently treated by the mixer high shear 2. The recirculation flow must be large enough to pump the entire volume through a high shear pump 6 more than 50 times. The production It can be discontinuously or continuously. Starch solution manufactured takes from the mixing tank / reserve 3 to a tank of major reserve 7.

The treatment time with the mixer raised shear 2 should usually be 5 minutes or more for a starch concentration of 5% by weight, and usually one hour or more for the starch concentration of 25% by weight. He modification time needed will be slightly longer for a continuous procedure that for a procedure in discontinuous.

Example 1

A scale test of laboratory in which the starch solutions were prepared both static, in which the cationic starch powder was added gradually to a beaker with a mixer raised and in-line shear, in which starch powder cationic was gradually added to a solution pumped through of a high shear mixer. In static mode, the Total liquid volume was mixed continuously. In the mode in line, one had to ensure enough pass through the mixer high shear to achieve the desired effects. Be carried out the trial to assess the difference between static and online systems with respect to modification time necessary and to the effectiveness of the modification.

The cationic potato starch powder is mixed with sea water. Starch concentrations were varied and changes in viscosity were measured as a function of weather. The production temperature was approximately 60 to 80 ° C and after mixing, the solutions were cooled to 20 ° C. Be tested the products as coagulants / flocculants on water Pulp and paper residuals using jar tests. The pitcher test conditions were 30 sec mixing at speed high (500 rpm), 10 min mixing at low speed (50 rpm) and 15 settling min. The conditions of starch modification and The results are presented in Table 1.

Table 1 presents the test conditions and the results from a laboratory scale test (static and online system) with relationships between concentration of starch, various modification times, final viscosity at 20 ° C, and the results of the product quality tests of starch as a flocculant coagulant in pulp wastewater and of paper.

TABLE 1

Mixer laboratory of Power 0.25 kW Static Static Static In line Online high shear (Silverson) Concentration % starch in 4.8 9.1 18.7 9.7 18 weight Volume Liter 0.8 0.7 one one one Time of mod. Minutes 25 25 55 38 113 Final viscosity cP (mPa s) 76 535 6500 455 3900  \ begin {minipage} [t] {45mm} Quality of starch product as a coagulant / flocculant in wastewater of pulp and of paper \ end {minipage}  \ begin {minipage} [t] {23mm} Effect of elimination of turbidity \ end {minipage} Excellent Good Moderate Good Excellent

As can be seen in the Table, the time of required modification increased with increasing concentration  of starch powder. The modification time required was slightly longer in an in-line mixer in which the starch solution was recirculated through the mixer high shear than in a shear mixer system high static The Table shows that the modification time insufficient, as measured by product quality as coagulant / flocculant, results in a higher viscosity. He Desired modification time in a scale production plant industrial will be regulated by the production system, the Product functionality and product handling.

Example 2

Starch modification assays are carried out in a 1 liter beaker with a static mixer with sufficient treatment time to achieve the desired starch quality with respect to the effect as coagulant / flocculant referred to as "Excellent" in the Example 1. Cationic potato starch powder was gradually added to seawater until concentrations of approximately 5% by weight, 10% by weight and between 17 and 20% in weight. The production temperature was approximately 60-80 ° C. The solutions were cooled to 40, 30 and 20 ° C, and at each temperature the viscosity for solutions was measured different.

Fig. 2 shows the relationship between the starch concentration and viscosity at 20, 30 and 40 ° C with water Marine used as the brine solution. As you can see in the Figure, a concentration of starch of approximately 10% by weight provides viscosities in the range between 300 and 600 cP (mPa s). Starch concentrations of approximately 17 to 20% by weight provide viscosities in the range between 2,000 and 7,000 cP (mPa s). Inside of the same concentration range of starch, the viscosity is more high when the temperature is 20ºC and the viscosity values Lower ones are obtained at 40 ° C. Usually the viscosity Increases with decreasing temperatures.

Example 3

Three different concentrations of starch solutions were prepared by mixing cationic potato starch powder with seawater. The concentrations of the starch solutions were 10% by weight, 15% by weight and 20% by weight. Two different starch solutions were prepared by mixing the cationic potato starch powder with a CaCl 2 solution of 20 g / l. The concentrations of the starch solution were 15% by weight and 20% by weight. The functionality of these five starch solutions was compared by the pulp mill and paper wastewater jar tests. Jug tests were carried out in 1 liter beakers mixing for 30 sec (500 rpm), 10 min of flocculation (50 rpm) and 15 min of sedimentation. The dosage of the starch solutions corresponded to between 20 and 120 ppm as starch (not as ppm of the solutions).
nes).

The starch solutions were processed for a period of between 20 and 40 minutes in 1 liter beakers with an elevated shear mixer. The temperature during mixing was approximately 60 to 80 ° C. The longer the processing time, the more effective the starch product is because of the more complete modification of the starch macromolecules. No improvements were achieved over a period of modification. With sufficient modification time, which depends on the concentration and production system, there should generally be no difference between the starch products produced with different brine solutions. After modification, the solutions were cooled to room temperature (20 ° C) and the products were tested as coagulants / flocculants on pulp and paper wastewater using a jaw test.
rra.

Fig. 3 shows the test results of jug on pulp and paper wastewater in which starch solutions 10% by weight, 15% by weight and 20% by weight are produced with seawater and 15% starch solutions in weight and 20% by weight with CaCl2 (20 g / l) respectively. The turbidity after coagulation / flocculation and sedimentation (FAU) is shown as a function of a dose of starch (ppm).

The results show that turbidity is effectively reduces already to 20 ppm and that the treatment efficiency Optimum is achieved at a dose of between 40 and 60 ppm of starch, which it is relatively quite favorable to the use of salts of metal. There is no significant difference in product quality as a coagulant / flocculant when seawater is used or CaCl2 as brine solution. The variation in turbidity between the different products is probably a result of a insufficient modification of cationic starch.

Example 4

An assay was carried out to compare the functionality of starch solutions produced in a glass of 1 liter precipitates with a static mixer versus a starch solution produced on an industrial scale with a mixer online. In addition, starch concentrations were significantly different to study how this affects the Starch product functionality as coagulant / flocculant. Be produced a 0.5% by weight starch solution with a mixer static in a 1 liter beaker and a solution of 18% starch by weight with one in line in a scale plant industrial as illustrated in Fig. 1. A solution of 0.5% starch by weight even though such low concentration does not It will be of practical use. In both solutions, starch powder of cationic potato was mixed with seawater and the time of modification was enough to achieve optimal functionality of the product as coagulant / flocculant, approximately 2 minutes for the 0.5% solution by weight on a laboratory scale and approximately one hour for the 18% solution by weight in plant Industrial scale The temperature during mixing was between 60 and 80 ° C and after mixing the solutions cooled to room temperature (20 ° C) and tested as coagulants / flocculants on pulp and paper wastewater with pitcher trials.

Fig. 4 shows the test results of jug with pulp mill and paper wastewater with 18% by weight starch solution produced with a mixer in industrial scale line (in line) and with starch solution 0.5% by weight produced in a 1 liter beaker with a static mixer (laboratory scale, discontinuous). The turbidity after flocculation and sedimentation (FAU) is shown as a function of the dose of starch (ppm). As can be seen in Figure, starch products produced on a scale of laboratory and industrial scale with concentrations significantly different are in good agreement. This means that product functionality is not sensitive to production process or the concentration of the solution of starch.

Example 5

A test was carried out on a scale plant industrial (as shown in Fig. 1) to study the effect of the cationic starch powder feed and the time of viscosity and temperature treatment. There was a 15% by weight starch solution from cationic powder of Potato starch and seawater. Potato Starch Powder cationic was added batchwise to the solution. The solution is cooled between each addition of starch powder.

Fig. 5 shows the relationship between the time of treatment (minutes), temperature (ºC) and viscosity (cP (mPa s)) in the production of a 15% solution of starch by weight in water Marine. In Fig. 5 it is seen that the viscosity increases with each addition of starch powder and that decreases quite quickly as result of high shear mixing. Temperature gradually increases with treatment time, but increases by usually more at high viscosity in a powder addition of starch. In an industrial scale plant it will be important find the right balance between feed rate of starch powder, viscosity and increased temperature.

The product according to the present invention is excellent as a coagulant / flocculant for water treatment and of wastewater alone or in combination with other products Chemicals For the treatment of municipal wastewater, You can typically combine the product with a minimum dose of salt metal (ferric or aluminum) to achieve good results with a lower sludge production. For pulp effluents and of paper, works well alone or can be combined with a flocculant, for example polyacrylamide or activated silica, to increase the sludge separation. For dairy effluents and for water that contain oil, shows excellent performance along with the activated silica

The benefits of the product and the procedure of production are lower treatment costs relative to other available products based on starch. The product provides improved water and water treatment residual The product is also ecological, biodegradable and Safe for handling, its pH is neutral and does not include toxic components

Claims (11)

1. Product for the treatment of water and wastewater, characterized in that said product comprises highly cationic starch powder dissolved in a brine solution comprising seawater and / or salts comprising ions of two valences, in which the chains of Dissolved starch polymer are cut into shorter units. 2. Product according to claim 1, characterized in that the salts are CaCl2 and / or Ca (NO3) 2 and / or MgCl2. 3. Product according to claim 1 or 2, characterized in that the concentration of the brine solution is from 5 to 50 g / l, preferably from 10 to 40 g / l. 4. Product according to any of the preceding claims, characterized in that the cationic starch powder has> 10% charge density (degree of substitution). 5. Product according to any of the preceding claims, characterized in that the starch powder is potato starch. 6. Product according to any of the preceding claims, characterized in that the concentration of starch is 5 to 25% by weight, preferably 15 to 25% by weight. 7. Product according to any of the preceding claims, characterized in that the viscosity is from 300 to 10,000 cP (mPa s), preferably from 1,000 to 5,000 cP (mPa s). 8. Method of producing a product for the treatment of water and wastewater, characterized in that a highly cationic starch powder and a brine solution comprising seawater and / or salts comprising ions of two valences in a mixer are mixed high shear in which the dissolved starch polymer chains are cut into shorter units to maintain viscosity <10,000 cP (mPa s) at temperatures> 15 ° C. 9. Method according to claim 8, characterized in that the viscosity is maintained at between 1,000 and 5,000 cP (mPa s). 10. The method according to claim 8 or 9, characterized in that the feed rate of powder to liquid is> 100 kg / m 3 h. Method according to any one of claims 8 to 10, characterized in that the production temperature is 50 to 100 ° C, preferably 60 to 80 ° C.